Process for aerating liquids in the production of yeast



y 1938- B. L. M. VAN DER LANDE ET AL 2,119,188

PROCESS FOR AERATING LIQUI DS IN THE PRODUCTION OF YEAST Filed Dec. 27, 1955 5AM; BY 5% Q11, *5

ATTORNEYS MT'eo-Jlm Patented May 31, 1938 PROCESS FOR, AERATING LIQUIDS IN- THE PRODUCTION OF YEAST Bernardus Lebuinus Maria, van der Lande and Emile van Thiel, Compiegne, France, assignors to Naamlooze venootschaplndustrieele Maat- .schappij Voorheen Noury &Van Der Lande, Dcventer, Netherlands, acompany of the Netherlands I Application December 27, 1935, Serial No. 56,400

In the Netherlands December 29, 1934 3 Claims.

The present invention relates to the aerating process in the production of yeast, by introducing into a nutrient medium oxygen gas as it ocours in ordinary air or oxygen enriched air.

fermenting liquid, in order to make the subdivision of the air still finer, so that the aeration process becomes still more efficient.

- It is a matter of course that preferably such 9 give more stable air-in-liquid suspensions.

, Suitable liquids are, for example, found amongst the liquids which are normally used in the manufacture of yeast. As an example, mof lass-es may be mentioned from which according liquids are used for making the dispersions which to the method described, stable air-in-liquid disp'ersions may be obtained.

If necessary, the molasses is diluted prior to the dispersion treatment and/or subjected'to a If necessary; we do not treat a part, but the whole liquid in this way.

The dispersing treatment may be utilized to add stimulants for the yeast propagating processes, for example, by adding substances, such as chloroform or toluol or organic acids, in small proportions, to the air in which the liquid is sprayed, the said proportions being so chosen, that they favourably influence the yeast propagating processes, when the air-in-liquid suspen- 5 It has been tried already inseveral ways, to purification or clarification process, in order to 5 cut down this large quantity of air, for example, facilitate the dispersion process. by blowing the air into the liquid throughplates Moreover, well-known stabilizers-for these susmade of ceramic material that have extremely pensionsmay'be added, for example, carbohyfine pores. drates, sugars, glycerol, higher alcohols and oth- 10 According to another method air is pressed er emulsifying agents.- 10

into the fermenting liquid by means of ejectors; It is of course necessary, that thoseadded substill a newer method is to perform the fine divistances do not unfavourably affect the reac- I sion or the air in the fermenting liquid by means tlons t a t pl uhder circumstances p eof an agitator. vailing in the process or that they retard the mul-= All the processes hitherto applied possess the Unification of f are harmful to the p flp 0 15 important drawback, that large quantities of air the nr a they may not decrease have to be compressed, which requires an exthe fermentafive and reprodiwtion Power of the tremely high amount of power. It stands to Yeast 1 reason that the costs of production are markedly further found t at the stability of the 2 increased by this high consumption of power, air-in-liquid suspensions is also dependent on the We have, now f d that air may be supplied hydrogen ion concentration, so that the dispersto the nutrient liquids, in a very economic way, mg proces? preferably carried out at u a i. e., with the smallest possible consumption of. hydrogen concentration liquid that power, by introducing the air into the said liqstablest air'in'hqmd suspenswm are uids in the form of an .air-in liquid dispersion tamed 25 manufactured in a special manner. We have pracnce preferably,such substances W111 be found that by Spraying a suitable liquid in air, sub ected to the dispersing process, that belong referably of atmospheric pressure and cbnect to the classes of substances which, for other rea- 'ng the mist thus obtained, an air-in-liquid dis- 2 22: $3;:g gig ig ggs g gg gl gg g sg 30 g'fi g gg gg a t g f fgg ig either as nutrient liquid for or tostimulate the that is: the bubbles of air are very small and zijropaga'tmn of the yeastto Controlthe hydmgen' therefore the air introduced has a large surface. 1%;?gifiggfi g' g fiz fiz r f z gg ggg If such a dispersion is added to a liquid in which one of these puposes,

5 yeast is growing, the air bubbles owing to their In l production of yeast We may utilize smallness vfery slowly to the surface h molasses whether or not. diluted with water, fermenting hqmd the Oxygen 9 the whether or not clarified as liquid for dispersing for this reason utilized to a much higher degree the am than in the processes hitherto known in which We may also withdraw a part of the liquid. 40 the air is introduced into the fermenting liquid subject this part to the dispersing process, after escapes rapidly. i i if desired, having it wholly or partlyfreed from If desired. the air-m-liqilld suspenslqn may yeast, to collect the dispersion and to add the airagain Subjectei p P moretlmesi to iii-liquid suspension thus obtained to the fer 4 the same operation before being added to the menting1iquid v sion is added to the fermenting liquid. The air may be sterilized before being emulsified, e. g., by heating.

A suitable apparatus for manufacturing the air-in-liquid dispersion used in our process is illustrated inthe accompanying drawing; a description of the various elements of the apparatus illustrated by the drawing will-be given at this point. in order to enable a more perfect understanding of our invention and the preferred method of carrying it out. a is a bowl of nearly cylindric form, with convex sidewalls. The bowl 1. is mounted on a shaft b that makes 5,000-12,000 revolutions per minute. At the top of the bowl a number of rings is mounted and connected with each other in such a way, that between them extremely narrow orifices are left, for example 0.1 mm. Depending on the method of connecting the rings these orifices may have a round, an oblong, or another form.

In operating the apparatus the liquid .to be dispersed is allowed to enter into the rotating bowl through the funnel d. The liquid is subjected to a centrifugal action by which any sludge that might be present and that would clog up the orifices between the rings is separatedfrom the liquid and collected in the convex parts of the bowl. The sludge-free liquid mounts to the top of the bowl where it is thrown through the narrow apertures and leaves the bowl in the form of extremely fine droplets. The droplets are -thrown at a. very high speed into the air chamber e surrounding the bowl. In this air cham her the particles of liquid collide withthe airplacement of the dispersed air' can fiow freely through an opening 1 or through the opening through which the funnel is passing in e.

A specific example of the liquid which we may use in preparing our air-liquid suspension, is beet sugar molasses diluted with water to aspecific gravity of 1.10. To this molasses we add 1 gram of dextrin per kilogram of the diluted molasses the said substance acting as a stabilizer. We further adjust the pH of the solution by adding alk'ali or acid until its value lies between 4.8 and 5.4. We may also add to the air such an amount of toluol that each kilogram of the air-inliquid dispersion after treatment contains 0.001

"gram of toluol that acts as a stimulant.

We withdraw preferably continuously from the total mass of fermenting solution of glucose regularly at the top of the fermentation vessel a, small percentage, we subject it to the dispersing treatment described and we introduce the air-in-liquid suspension obtained at the bfittom of the feimentation vessel into the fermenting liquid. This operation is carried out at such a speed that every hour the whole of the fermenting liquid passes through the dispersing apparatus.

The dimensions of the air-bubbles are from A mm. to a few microns. The suspensioncollected from the apparatus in the above described method is a milky liquid and breaks slowly with the liberation of air. If this suspension is placed in a,test tube about one half minute elapses, before at the bottom of the tube a separation of the dispersion into the components becomes visible by a beginning clearing up of the liquid.

When it is considered, that in the manufacture of yeast the height of the liquid in the fermenting vessel is often 3-4 meters it is clear that the air bubbles, that areintroduced into the liquid at the bottom and in form of the said liquid-air suspension or emulsion that is to say, a two component colloidal system consisting of a liquid as the external or continuous phase and air as the disperse or internal phase, would require a long time to traverse the liquid from bottom to top, thereby, can be utilized to a much higher degree than air introduced in the form of the usual air bubbles,.formed by passing air through some sort of porous or perforated material which traverse the liquid in a few seconds.

this air need not be finely divided. This air may be, say 5% of that required for the yeast undergoing propagation.

' Numerous modifications 'of our invention are within-the scope of the present specification. For example, instead of using molasses, commercial glucose or the substances specifically mentioned herein as the external phase of the air-in-liquid suspension or emulsion, we may use water containing emulsifying agents such as gelatin, agaragar and the like. Or gelatin and agar-agar may be used as stabilizers of a molasses solution air emulsion.

What we claim is:

1. A process for propagating yeast which comprises introducing yeast cells into a nutrient medium comprising molasses and aerating the yeast by introducing into the nutrient medium containing the yeast a separately prepared air-in-liquid dispersion made by centrifuging a dilute molasses solution and rapidly projecting it into an air space where it collides with and envelops particles of air to produce a stable air-in-liquid dispersion 

